This invention relates to a device for injecting fuel into an intake air supply passage which is communicated with the combustion chambers of an internal combustion engine.
It is well known to inject fuel by means of a fuel injector into an intake air passage at a position upstream of a throttle valve which is utilized to adjust the flow of an air fuel mixture so that the air fuel mixture can be prepared and supplied to an internal combustion engine. When fuel is injected by means of such a conventional fuel injector, almost all of the injected fuel will adhere onto an internal surface of the intake air supply passage, a so-called throttle bore, and, then, the adhering fuel will flow downwards along the internal surface. Since such downward flowing fuel cannot be readily admixed with the intake air to become atomized and vaporized, the unatomized and unvaporized fuel will often be taken into a combustion chamber through an intake pipe. As a result, according to the above-mentioned conventional injection type fuel supply system, due to the downward flowing of the fuel, the amount of intake fuel, between the engine cylinders and between the working cycles of the engine, may not be uniform, thereby causing difficulties when harmful contaminants contained in the exhaust gas emitted from an engine are reduced and also causing an unstable engine revolution.